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HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 2
Prepared by
Hydro Performance Processes Inc.
Doylestown, PA 18901-2963
and
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, TN 37831-6283
managed by
UT-BATTELLE, LLC
for the
U. S. DEPARTMENT OF ENERGY
under contract DE-AC05-00OR22725
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 3
Contents
1.0 Scope and Purpose ............................................................................................................... 4
1.1 Hydropower Taxonomy Position ..................................................................................... 4
1.1.1 Components of a Francis Turbine Aeration System ................................................. 4
1.2 Summary of Best Practices .............................................................................................. 8
1.2.1 Best Practices Related to Performance/Efficiency and Capability ...................... 8
1.2.2 Best Practices Related to Reliability and Operations & Maintenance ................ 8
1.3 Best Practice Cross-references ......................................................................................... 8
2.0 Technology Design Summary .............................................................................................. 9
2.1 Technology Evolution ...................................................................................................... 9
2.2 State of the Art Technology ........................................................................................... 10
3.0 Operation & Maintenance Practices .................................................................................. 12
3.1 Condition Assessment .................................................................................................... 12
3.2 Operations ................................................................................................................... 13
3.3 Maintenance ................................................................................................................ 14
4.0 Metrics, Monitoring, and Analysis .................................................................................... 15
4.1 Measures of Performance, Condition, and Reliability ................................................... 15
4.2 Data Analyses ................................................................................................................. 15
4.3 Integrated Improvements................................................................................................ 16
5.0 Information Sources: .......................................................................................................... 17
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 4
1.0 Scope and Purpose
This best practice for Francis turbine aeration addresses the technology, condition assessment,
operations, and maintenance best practices with the objective to maximize the unit performance
and reliability. The primary purpose of a Francis turbine aeration system is to provide air into the
turbine as a way of increasing the downstream dissolved oxygen (DO) level for environmental
enhancement.
Hydropower plants likely to experience problems with low DO include those with a reservoir
depth greater than 50 feet, power capacity greater than 10 MW, and a retention time greater than
10 days [3, 6]. In general, these include plants with watersheds yielding moderate to heavy
amounts of organic sediments and located in a climate where thermal stratification isolates
bottom water from oxygen-rich surface water. At the same time, organisms and substances in the
water and sediments consume and lower the DO in the bottom layer. For plants with bottom
intakes, this low DO water often creates problems downstream from the reservoir, including
possible damage to aquatic habitat. Most of the hydropower plants experiencing problems with
low DO have Francis turbines. Typically, the most cost-effective method for increasing the
downstream DO level is to use some form of Francis turbine aeration [9, 11].
A Francis turbine aeration system’s design, operation, and maintenance provide the most
significant impact to the efficiency, performance, and reliability for a hydro unit utilizing the
system. Aerating Francis turbines can experience insignificant to moderate (approx. 0.2% - 1%)
efficiency losses even without aeration due, for example, to baffles or thicker blades compared to
conventional, non-aerating technology. Aerating Francis turbines can experience significant (3%
to 10% or more) efficiency losses with aeration, depending on the amount of air introduced into
the turbine and the locations where the air is introduced [1, 2, 3, 4]. Francis turbines aerating
through existing vacuum breaker systems and Francis turbines retrofitted for aeration using hub
baffles typically experience restrictions in both capacity and flexibility that can significantly
reduce generation [1, 2, 3, 4, 5, 6, 9, 11, 12].
1.1 Hydropower Taxonomy Position
Hydropower Facility → Powerhouse → Power Train Equipment → Turbine → Francis
Turbine → Aeration Devices (Francis Turbine Aeration System)
1.1.1 Components of a Francis Turbine Aeration System
A Francis turbine aeration system can be either active or passive in design. An active
design includes some type of motorized blower or compressor to force air into the turbine
for mixing with water in the turbine and/or draft tube. The far more common passive
design emphasized in this best practice typically includes either (1) additions or
modifications to the turbine runner or draft tube to create zones of localized low pressure
and draw atmospheric air into the turbine (see hub baffles in Figure 1) or (2) a turbine
runner specifically designed for aeration (see Figure 2). The components of a Francis
turbine aeration system affecting performance and reliability typically consist of air
intakes, air flow instrumentation, sound mufflers, control valves, and air supply piping, as
shown in Figure 3.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 5
Figure 1: Photograph of Francis Turbine with Hub Baffles and Diagrams Showing Streamlined and Flat
Plate Baffles [6]
Figure 2: Sectional View of Francis Turbine with Central Aeration (Red, Vacuum Breaker; Blue, Shaft),
Peripheral Aeration (Yellow), and Distributed Aeration (Green) [9]
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 6
Figure 3: Typical Configuration for a Francis Turbine Aeration System [7]
Air Intakes: Properly designed air intakes, typically bellmouths, reduce the noise levels
associated with the air flow and reduce pressure losses in the aeration system, which
increases air flow through the aeration system. If a standard nozzle design is used for the
intake or if the intake is properly calibrated, the intake can also be used for air flow
measurement (see Figure 4), which is discussed in the following section.
Air Flow Instrumentation: A variety of technologies can be used for air flow
measurements, including bellmouth inlets, Venturi meters, orifice plates, air velocity
traverses (typically using a Pitot-static tube or hot-film anemometer), calibrated elbow
meters (calibrate off-site with appropriate upstream piping or calibrate in place with
velocity traverses), and calibrated single-point velocity measurements (calibrate off-site
with appropriate upstream piping or calibrate in place with velocity traverses). The
following instruments may also be required for air flow measurements, depending on the
type of air flow meters selected for the aeration system:
Electronic differential pressure cells (preferred), manometers, or mechanical
differential pressure gages;
Thermometers, thermistors, RTDs, or thermocouples for air temperature
measurements at primary flow elements;
Barometer, mechanical pressure gage, or electronic pressure cell for air pressure
measurements at primary flow elements; and
Psychrometer or other means to determine relative humidity at primary flow
elements.
Bellmouth (typ.) for loss
and noise reduction
Bellmouth (typ.) for loss
and noise reduction
Control valveControl valve
Muffler for noise reductionMuffler for noise reduction
Section for measuring air flowSection for measuring air flow
Bellmouth (typ.) for loss
and noise reduction
Bellmouth (typ.) for loss
and noise reduction
Control valveControl valve
Muffler for noise reductionMuffler for noise reduction
Section for measuring air flowSection for measuring air flow
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 7
Figure 4: Inlet nozzle and differential pressure cell for determining air flow [7]
Detailed instructions, equations, and charts useful for understanding air flow
measurements are provided in ASME 1983 [14] and Almquist et al. 2009 [15]. Although
the performance test code for turbines and pump-turbines, ASME PTC 18-2011 [16],
does not currently include turbine aeration systems, a revision addressing aeration
systems is underway [13].
Sound Mufflers: The function of the sound mufflers is to reduce the noise levels
associated with air flows into the Francis turbine aeration system. A properly designed
muffler will reduce noise to a safe level without significantly decreasing the air flow.
Control Valves: The control valves are used to turn on or shut off the air flows into a
Francis turbine aeration system or to regulate the amount of air flow in the system.
Control valves may be manually operated, remotely operated, or integrated into the
plant’s control system.
Air Supply Piping: The Francis Turbine Best Practice discusses the role of the vacuum
breaker system for drawing in atmospheric air at low gate openings to reduce vibration
and rough operation. Due to the air piping sizes in typical vacuum breaker systems, a
retrofitted vacuum breaker system, even with the addition of hub baffles, rarely supplies
enough air to produce a significant increase in downstream DO. Both retrofitted aeration
systems and aerating turbines typically require additional air supply piping, as shown in
Figures 2 and 3.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 8
1.2 Summary of Best Practices
1.2.1Best Practices Related to Performance/Efficiency and Capability
Best practices related to performance/efficiency and capability are similar to the
Francis Turbine Best Practice, with the addition of aerating operation:
Establish accurate current unit performance characteristics and limits under
both aerating and non-aerating conditions through periodic testing [13, 16].
Disseminate accurate unit performance characteristics under both aerating and
non-aerating conditions to unit operators, local and remote control systems,
decision support systems, and other personnel and offices that influence unit
dispatch or generation performance.
Conduct real-time monitoring and periodic analyses of unit performance under
both aerating and non-aerating conditions at Current Performance Level (CPL) to
detect and mitigate deviations from expected efficiency for the Installed
Performance Level (IPL) due to degradation or instrument malfunction.
Periodically compare the CPL under both aerating and non-aerating conditions to
the Potential Performance Level (PPL) under both aerating and non-aerating
conditions to trigger feasibility studies of major upgrades.
Maintain documentation of CPL under both aerating and non-aerating conditions
and update when modification to the equipment (e.g., hydraulic profiling, unit
upgrade) or the aeration system (e.g., additional air piping, modifications to hub
baffles or draft tube baffles, aerating unit upgrade) is made.
1.2.2Best Practices Related to Reliability and Operations & Maintenance
Use ASTM A487 / A743 CA6NM stainless steel to manufacture Francis turbine
runners to maximize resistance to cavitation and cavitation-enhanced corrosion.
Clad aeration discharge areas with stainless steel to mitigate cavitation-enhanced
corrosion.
Monitor trends for air flows under similar operating conditions to detect aeration
system problems.
Routinely inspect air intakes, mufflers, air piping, and air outlets and remove any
obstructing debris for optimal performance.
1.3 Best Practice Cross-references
I&C - Automation Best Practice
Mechanical – Francis Turbine Best Practice
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 9
2.0 Technology Design Summary
2.1 Technology Evolution
In the 1950s, turbine venting through the vacuum breaker system was introduced in
Wisconsin to reduce the water quality impact of discharges from the pulp and paper industry
and from municipal sewage systems. Research was also conducted in Europe to develop
turbine designs that would boost dissolved oxygen levels in water passing through low head
turbines. By 1961, turbine aeration systems were operating in the U. S. at eighteen
hydroplants on the Flambeau, Lower Fox, and Wisconsin. During the late 1970s and early
1980s, the Tennessee Valley Authority (TVA) developed small, streamlined baffles, called
hub baffles, which reduced energy losses while increasing air flows and operating range for
aeration. The hub baffles installed at TVA’s Norris Project (see Figure 1) provided DO
uptakes averaging 2 to 3 mg/L with typical efficiency losses of 1 to 2% [1].
During the mid-1980s, Voith Hydro Inc. and TVA invested in a joint research partnership to
develop improved hydro turbine designs for enhancing DO concentrations in releases from
Francis-type turbines. Scale models, numerical models, and full-scale field tests were used in
an extensive effort to validate aeration concepts and quantify key parameters affecting
aeration performance. Specially-shaped geometries for turbine components were developed
and refined to enhance low pressures at appropriate locations, allowing air to be drawn into
an efficiently absorbed bubble cloud as a natural consequence of the design and minimizing
power losses due to the aeration. TVA’s Norris Project, which was scheduled for unit
upgrades, was selected as the first site to demonstrate these “auto-venting” or “self-aerating”
turbine technologies. The two Norris aerating units contain options to aerate the flow through
central, distributed, and peripheral air outlets, as shown in Figure 2.
The successful demonstration of multiple technologies for turbine aeration at TVA’s Norris
Project in 1995 has helped to develop market acceptance for aerating turbines. Major turbine
manufacturers who currently offer aerating turbines include ALSTOM, American Hydro,
Andritz, and Voith Hydro.
Performance levels for aerating turbine designs can be stated at three levels as follows:
The Installed Performance Level (IPL) is described by the unit performance
characteristics at the time of commissioning, under aerating and non-aerating
conditions. These may be determined from reports and records of efficiency and/or
model testing conducted prior to and during unit commissioning.
The Current Performance Level (CPL) is described by an accurate set of unit
performance characteristics determined by unit efficiency and air flow testing, under
aerating and non-aerating conditions. This requires the simultaneous measurement of
water flow, air flow, head, and power under a range of operating conditions, as
specified in the standards referenced in this document [14, 15, 16].
Determination of the Potential Performance Level (PPL) typically requires reference
to new aerating turbine design information from the turbine manufacturer to establish
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 10
the achievable unit performance characteristics of the replacement turbine under
aerating and non-aerating conditions.
2.2 State of the Art Technology
For aerating Francis turbines, turbine efficiencies under aerating and non-aerating conditions
are the most important factor in an assessment to determine rehabilitation and replacement,
as well as proper operation.
When properly designed, hub baffles typically reduce efficiency by 0.5% to 1% without
aeration and 5% or more with aeration, depending on the air flows [1, 2, 3, 4, 5, 9]. In the
cross-section through an aerating Francis turbine shown in Figure 2, central aeration through
the turbine’s vacuum breaker system is shown in red, and central aeration through the shaft is
shown in blue. Using an existing vacuum breaker system is typically the aeration option with
the lowest initial cost. However, central aeration has the largest effect on unit efficiency, and
the capacity and operational range for the turbine may be severely limited [1, 2, 3, 11, 12].
Figure 2 also shows peripheral aeration in yellow and distributed aeration through the trailing
edges of the turbine blades in green. Distributed aeration often has the smallest effect on unit
efficiency and the highest oxygen transfer into the water (i.e., increased DO), followed by
peripheral aeration [11, 12]. For example, a recent study compared the central, peripheral,
and distributed aeration systems needed to provide a 5 mg/L DO increase for a plant in the
southern USA [12]. In the vicinity of the maximum efficiency, the predicted air flow
requirements (i.e., void fraction in %) for central, peripheral, and distributed aeration systems
were 7.2%, 6.9%, and 6.5%, respectively. The corresponding efficiency decreases (i.e., non-
aerating efficiency minus aerating efficiency, in %) were greater than 10%, 7.4%, and 3.4%,
respectively. These predictions are consistent with field test results reported for other sites [6,
8, 11].
In another example, aerating and non-aerating performance testing was conducted according
to ASME PTC-18 standards [16] at a hydro plant with multiple types of aerating runners,
including two eighty-years-old original runners retrofitted for central aeration, two modern
runners installed in 2002 and designed for central aeration, and four state of the art runners
installed in 2008 with distributed aeration (see Figure 5) through the trailing edges of the
runners [11]. Figure 6 shows the aerating and non-aerating turbine efficiencies versus turbine
outputs for the three unit types at this plant, operating at a net head of 95 ft. The turbine
efficiencies have been normalized to the maximum measured efficiency of the most efficient
unit.
In Figure 6, note the relative efficiencies for the three unit types, the relative effects of
aeration on efficiency for central and distributed aeration systems, and the relative amounts
of air aspirated by the three unit types. Under non-aerating operation, the 2008 replacement
runners (distributed aeration) have the highest peak efficiency, with both the original turbines
(retrofitted central aeration) and the 2002 replacement runners (designed central aeration)
about 4% lower.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 11
Figure 5: State of the Art Aerating Turbine with Distributed Aeration
Figure 6: Normalized Turbine Efficiencies versus Turbine Output for Three Unit Types [11]
Net Head Efficiency Test Results (Central and Distributed Aeration)Net Head = 95 ft
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
10 15 20 25 30 35 40
Turbine Output (MW)
No
rma
lize
d N
et
He
ad
Tu
rbin
e E
ffic
ien
cy
2002 Upgraded Unit, Central Aeration Off
2002 Upgraded Unit, Central Aeration On (Qa/Qw = 2.7% to 4.4%)
Original Unit, Central Aeration Off
Original Unit, Central Aeration On (Qa/Qw = 0% to 3.1%)
2008 Upgraded Unit, Distributed Aeration Off
2008 Upgraded Unit, Distributed Aeration On (Qa/Qw = 5.0% to 7.4%)
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 12
Under aerating operation, peak efficiencies for the 2008 replacement runners, the 2002
replacement runners, and the retrofitted original units drop by about 2.5%, 7%, and 2% (with
very low air flows for the retrofitted original units), respectively. Air flow to water flow ratio
ranges under aerating operation for the 2008 replacement runners, the 2002 replacement
runners, and the retrofitted original runners are 5.0% to 7.4%, 2.7% to 4.4%, and 0% to
3.1%.
The operational challenges for efficient power operation and effective environmental
operation of the plant’s eight units under non-aerating and aerating conditions, over a range
of heads, and with rapid load swings are apparent, emphasizing the importance of proper
control system design [11].
3.0 Operation & Maintenance Practices
3.1 Condition Assessment
After the commercial operation begins, how an aerating Francis turbine is operated and
maintained will have a major impact on reducing efficiency losses and maintaining
reliability. Materials for turbine runners are usually cast iron, steel, or stainless steel. As a
best practice, the most common material being used today for new state of the art runners is
ASTM A487 / A743 CA6NM stainless steel (see Francis Turbine Best Practice).
Aeration systems for Francis turbines can take the form of more complex and more energy-
consumptive active systems, such as motorized blowers, to the less complex passive systems,
such as baffles and aerating runner designs. Focusing on the most common aeration system
designs (i.e., passive systems), a simple condition assessment includes inspections of the air
intakes, the air discharge passages in the turbine, the dissolved oxygen monitoring
equipment, and any observable cavitation or corrosion-related damage that might affect
normal operation. A decrease in the expected dissolved oxygen uptake in the waterway
downstream from the plant is a good indicator of degradation in the condition of the aeration
device.
A comprehensive condition assessment for a Francis turbine aeration system requires
information on:
(1) the plant’s environmental and regulatory environment, including
incoming DO, TDG, and water temperature levels throughout the year
measurement locations and methods for incoming DO, TDG, and temperature
(typically, multiple locations in penstock or spiral case)
regulatory requirements for downstream DO, TDG, and temperature
measurement locations and methods for downstream DO, TDG, and temperature
record of compliance and non-compliance;
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 13
(2) the plant’s operational environment, including
daily and seasonal operational patterns
typical tailwater range during periods of aeration
other restrictions affecting operations (e.g., rough zones, special requirements for
functioning of aeration systems);
(3) details of the specific aeration system, including
type of aeration system (e.g., vacuum breaker, hub baffles, central, peripheral,
distributed, multiple methods)
diameters and lengths of aeration piping
control valve characteristics;
(4) environmental and hydraulic performance of the specific aeration system, including
pressures at aeration outlets over the operational range
head losses for the aeration piping
air flows through the aeration piping as a function of tailwater elevation, water
flow, and control valve position
turbine efficiency without aeration as a function of power and head
turbine efficiency with aeration as a function of power, head, and air flow
DO uptake over the range of operational conditions
Corresponding TDG levels over the range of operational conditions.
3.2 Operations
Because aerating Francis turbines typically have a narrow operating range for peak efficiency
(see Figure 6, for example), it is extremely important to provide plant operators or automated
control systems with accurate operating curves for the units under aerating and non-aerating
conditions. The curves usually originate from the manufacturer’s model test data and from
post-installation performance testing. Because turbine performance can degrade over time,
periodic performance testing must be carried out to determine unit efficiencies and to update
the performance curves used for operational decisions. The ten-year testing cycle
recommended in the Francis Turbine Best Practice is typically appropriate.
Francis turbine aeration systems may be operated manually or the operation may be
integrated into a plant’s control system. The detailed aeration instrumentation and controls
are site-specific. Aeration systems are often operated conservatively to ensure that
environmental requirements for DO levels are maintained. However, this can lead to higher
levels of total dissolved gases (TDG), as well as unnecessary efficiency losses due to
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 14
excessive air flows into the turbine. Some sites have TDG environmental requirements in
addition to DO requirements, and the TDG requirements can have an additional negative
impact on plant operation and further reduce overall plant efficiency [11].
3.3 Maintenance
For Francis turbine aeration systems, all air flow intakes and passageways must be clean and
free from obstructions to operate properly. Normal maintenance of a Francis turbine aeration
system includes periodic inspection (during routine inspections) and testing of components to
ensure that the aeration system is operating according to design. Areas adjacent to the air
discharge locations in the turbine or draft tube must be monitored for damage due to
cavitation-influenced corrosion. As a best practice, the area surrounding the air discharge
locations should be clad with stainless steel to mitigate damage.
The associated instrumentation for Francis turbine aeration systems, including incoming DO
levels, compliance point DO levels, air flow rates, air valve control, and air valve positions,
must be calibrated and maintained in good working order. Instrumentation for hydraulic
performance data, including unit water flow rates, headwater elevations, tailwater elevations,
and unit powers, must also be calibrated and maintained in good working order. Data on
incoming DO levels, air valve positions, air flow rates, and air temperatures should be
recorded at time intervals that can be correlated with other relevant plant data. As a best
practice, hydraulic performance data and environmental performance data (incoming DO
levels, compliance point DO levels, compliance point TDG levels, unit air flow rates, air
temperatures) should be simultaneously recorded and stored in a common database.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 15
4.0 Metrics, Monitoring, and Analysis
4.1 Measures of Performance, Condition, and Reliability
The fundamental performance measurement for a hydro turbine is described by the efficiency
equation, which is defined as the ratio of the power delivered by the turbine to the power of
the water passing through the turbine. The general expression for this efficiency (η) is
where P is the output power, ρ is the density of water, g is the acceleration of gravity, Q is
the water flow rate through the turbine, and H is the head across the unit [16].
The condition of an aerating Francis turbine can be monitored by the Condition Indicator
(CI) as defined according to the HAP Condition Assessment Manual [10].
Unit reliability characteristics, as judged by the unit’s availability for generation, can be
monitored by use of the North American Electric Reliability Corporation (NERC)
performance indicators, such Equivalent Availability Factor (EAF) and Equivalent Forced
Outage Factor (EFOR), which are used universally by the power industry [17]. However,
hydro plant owners typically do not designate whether or not their Francis turbines are
aeration-capable and do not differentiate between aerating and non-aerating operation.
4.2 Data Analyses
The key measurements for hydraulic performance include headwater elevation, HHW (ft);
tailwater elevation, HTW (ft); water flow rate through Unit N without aeration, QN (cfs);
power output for Unit N without aeration, PON (MW); and TH, the measurement timestamp
for hydraulic data. The key measurements for environmental performance include incoming
DO level for Unit N, LDON (mg/L); incoming TDG level for Unit N, LTDGN (%); incoming
water temperature, FWTN (degrees F); downstream DO level for plant at the compliance
location, LDOC (mg/L); downstream TDG level, LTDGC (%) at the compliance location; and
downstream water temperature, FWTC (degrees F), at the compliance location; air flow rate
through Unit N, QAN (cfs); water flow rate through Unit N with aeration, QNA (cfs); power
output for Unit N with aeration, PONA (MW); and TE, the measurement timestamp for
environmental data. Measurements can be near real-time or periodic (hourly, daily),
depending on the site details, license requirements, and operational requirements.
The unit efficiency ηN (nondimensional) for operation without aeration is:
ηN = PON/[KρgQN(HHW - HTW)/(1,000,000)]
where K is a dimensional constant, ρ is the density of water at Unit N, and g is the acceleration
of gravity at Unit N. For most cases, using Kρg = 84.5 provides satisfactory results.
The unit efficiency ηNA (nondimensional) for operation with aeration is:
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 16
ηNA = PONA/[KρgQNA(HHW - HTW)/(1,000,000)]
References provide detailed guidance on performing the key hydraulic measurements [16]
and the key environmental measurements [14, 15].
The unit efficiency loss due to aeration is equal to ηN minus ηNA for a given power level.
However, detailed data analyses are required to determine what portion of these efficiency
losses are avoidable, due to over-aeration, suboptimization, etc., and to compute the associated
revenue losses. In general, aeration-induced efficiency losses greater than 2% to 3% warrant
further investigation. The costs associated with the aeration-induced efficiency losses,
capacity losses, and reductions in operational flexibility should be established for comparison
with the associated revenue losses and used to optimize aeration operations and to evaluate and
justify new aeration systems, including turbine replacements.
The condition assessment of an aerating Francis turbine is quantified through the CI, as
described in the HAP Condition Assessment Manual [10]. The overall CI is a composite of
the CI derived from each component of the turbine. This methodology can be applied
periodically to derive a CI snapshot of the current turbine condition so that it can be
monitored over time and studied to determine condition trends that can impact performance
and reliability.
The reliability of a unit as judged by its availability to generate can be monitored through
reliability indexes or performance indicators as derived according to NERC’s Appendix F,
Performance Indexes and Equations [17].
4.3 Integrated Improvements
Data on lost efficiency, lost capacity, and operational restrictions due to Francis turbine
aeration systems can be used to quantify lost revenues from generation and ancillary services,
and the economic losses can be used to evaluate and justify funding for aeration system
improvements, including turbine replacement.
The periodic field test results should be used to update the unit operating characteristics and
limits. Optimally, the updated results would be integrated into an automated control system.
If an automated control system is not available, hard copies of the updated curves and limits
should be made available to all relevant personnel, particularly unit operators, and the
importance of the updated results should be emphasized, discussed, and confirmed.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 17
5.0 Information Sources:
Baseline Knowledge:
1. Bohac, C. E., J. W. Boyd, E. D. Harshbarger, and A. R. Lewis, Techniques for
Reaeration of Hydropower Releases, Technical Report No. E-83-5, Vicksburg,
Mississippi: U. S. Army Corps of Engineers, February 1983.
2. Wilhelms, S. C., M. L. Schneider, S. E. Howington, Improvement of Hydropower
Release Dissolved Oxygen with Turbine Venting, Technical Report No. E-87-3,
Vicksburg, Mississippi: U. S. Army Corps of Engineers, March 1987.
3. EPRI, Assessment and Guide for Meeting Dissolved Oxygen Water Quality
Standards for Hydroelectric Plant Discharges, Report No. GS-7001, Palo Alto,
California: ElectricPower Research Institute (EPRI), November 1990.
4. Carter, J., “Recent Experience with Hub Baffles at TVA,” ASCE Proceedings of
Waterpower 95, San Francisco, California, July 25-28, 1995.
5. EPRI, Maintaining and Monitoring Dissolved Oxygen at Hydroelectric Projects:
Status Report, Report No. 1005194, Palo Alto, California: Electric Power Research
Institute (EPRI), May 2002.
State of the Art:
6. Hopping, P. N., P. A. March and P. J. Wolff, “Justifying, Specifying, and Verifying
Performance of Aerating Turbines,” Proceedings of HydroVision 98, Reno, Nevada,
July 28-31, 1998.
7. March, P. A., R. K. Fisher, and V. G. Hobbs, “Water and Energy Infrastructure:
Meeting Environmental Challenges for a Sustainable Water and Energy Future,”
USACE 2003 Infrastructure Systems Conference, Las Vegas, Nevada, May 6-8,
2003.
8. Foust, J. M., R. K. Fisher, P. M. Thompson, M. M. Ratliff, and P. A. March,
“Integrating Turbine Rehabilitation and Environmental Technologies: Aerating
Runners for Water Quality Enhancement at Osage Plant,” Proceedings of
Waterpower XVI, Spokane, Washington, July 27-30, 2009.
9. March, P. A., Hydropower Technology Roundup Report: Technology Update on
Aerating Turbines, Report No. 1017966, Palo Alto, California: Electric Power
Research Institute, 2009.
10. ORNL et al., HAP Condition Assessment Manual, October, 2011.
11. March, P. A., “Hydraulic and Environmental Performance of Aerating Turbine
Technologies,” EPRI-DOE Conference on Environmentally-Enhanced Hydropower
Turbines: Technical Papers, Palo Alto, California: Electric Power Reaearch
Institute (EPRI) and Washington, D.C.: U. S. Department of Energy (DOE), Report
No. 1024609, December 2011.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 18
12. Foust, J. M., and S. Coulson, “Using Dissolved Oxygen Prediction Methodologies
in the Selection of Turbine Aeration Equipment,” EPRI-DOE Conference on
Environmentally-Enhanced Hydropower Turbines: Technical Papers, Palo Alto,
California: Electric Power Reaearch Institute (EPRI) and Washington, D.C.: U. S.
Department of Energy (DOE), Report No. 1024609, December 2011.
13. Kirejczyk, J., “Developing Environmental Standards and Best Practices for
Hydraulic Turbines,” EPRI-DOE Conference on Environmentally-Enhanced
Hydropower Turbines: Technical Papers, Palo Alto, California: Electric Power
Reaearch Institute (EPRI) and Washington, D.C.: U. S. Department of Energy
(DOE), Report No. 1024609, December 2011.
Standards:
14. ASME, Fluid Meters: Their Theory and Application, New York, New York:
American Society of Mechanical Engineers (ASME), 1983.
15. Almquist, C. W., P. N. Hopping, and P. J. Wolff, “Draft Test Code for Aerating
Hydroturbines,” TVA Report No. WR98-1-600-125, Norris, Tennessee: Tennessee
Valley Authority (TVA), August 1998.
16. ASME, Performance Test Code 18: Hydraulic Turbines and Pump-Turbines,
ASME PTC 18-2011, New York, New York: American Society of Mechanical
Engineers (ASME), 2011.
17. NERC, Appendix F: Performance Indexes and Equations, January 2011.
It should be noted by the user that this document is intended only as a guide. Statements are of a
general nature and therefore do not take into account special situations that can differ
significantly from those discussed in this document.
HAP – Best Practice Catalog – Francis Turbine Aeration
Rev. 2.0, 10/12/2012 19
For overall questions
please contact:
Brennan T. Smith, Ph.D., P.E.
Water Power Program Manager
Oak Ridge National Laboratory
865-241-5160
or
Qin Fen (Katherine) Zhang, Ph. D., P.E.
Hydropower Engineer
Oak Ridge National Laboratory
865-576-2921